Removing Stains From Concrete
Content
While practically every type of stain can be removed from concrete, eradication of old, long neglected stains may require
patience. It is often a matter of repeating the treatment until the desired results are attained. When the staining matter is
unknown, the treatment may require some experimentation. Many chemicals may be applied to concrete without appreciable injury, but acids or chemicals having an acid reaction should be avoided. Even weak acids may roughen the surface
if left for any length of time. For stains which penetrate, it is necessary to resort to
poultice or bandage. A poultice made by mixing active chemicals with fine inert powder
Treatment of Iron Stains
to a pasty consistency is applied in a thick layer. Bandages consist of cotton batting, or
layers of cloth, soaked in chemicals and pasted over the stain.
Iron Stains can usually be recognized by
their resemblance to iron rust, or by their
t
proximity to steel or iron in the building.
righ
y
p
Large areas stained from using curing waCo
ter containing iron may be improved in
Ink Stains
Tobacco Stains
appearance by mopping with a solution
Different inks require different
The following formula is generally
containing 1-pound oxalic acid powder
treatments. Ordinary writing inks may
effective: dissolve 2 pounds of trisodium
per gallon of water. After 2 or 3 hours,
etch concrete due to acid content. To
phosphate crystals in 1 gallon of hot
rinse with clear water, scrubbing at the
remove a stain of this type, make a strong
water. Mix 12 ounces of chlorinated
same time with stiff brushes or brooms.
solution of sodium perborate in hot
lime to a paste in a shallow enameled
Bad spots may be scrubbed with a second
water. Mix with whiting to a thick paste,
pan by adding water slowly and mashing
application. For deeper stains, the followapply in ¼-inch layer, and leave until dry.
the lumps. Pour this and the trisodium
ing methods may be used.
If some of the blue color is visible after
phosphate solution into a 2-gallon
Method 1: Dissolve 1 part sodium cithe
poultice
is
removed,
repeat.
If
only
a
stoneware jar and add water until full.
trate in 6 parts water. Mix thoroughly
brown stain remains, treat it by Method
Stir well, cover the jar and allow the lime
with equal volumes of glycerin. Mix part
1 for iron stains. Sodium perborate can
to settle. To use, add some of the liquid
of this liquid with whiting to form a paste
be obtained from any druggist.
to powdered talc until a thick paste is
just stiff enough to adhere to the surface
Many red, green, violet and other
obtained. Apply with a trowel as a ¼in a thick coat. Apply with a putty knife
bright colored inks are water solutions
inch poultice. To apply with a brush,
or trowel; this will dry in a few days. It
of synthetic dyes. Stains made by this
add about one teaspoon of sugar to each
should then be replaced with a new layer,
type of ink can usually be removed by
pound of powdered talc. When dry,
or softened by addition of more liquid.
the
sodium
perborate
poultice
described
scrape off with wooden paddle or trowel.
While this treatment has no injurious
above. Often the stain can be removed
This mixture is a strong bleaching agent
effects, its action may be too slow to be
by applying ammonia water on cotton
and is corrosive to metal. Care should be
practical with bad stains. Ammonium
batting. Javelle water is also effective,
taken not to drop it on colored fabrics or
citrate may produce quicker results than
used the same as ammonia water, or
metal fixtures.
sodium citrate, but may injure polished
mixed to a paste with whiting and applied
This method is valuable for treating
surfaces slightly.
as poultice. A mixture of equal parts of
other stains. Trisodium phosphate may
Method 2: For deep and intense iron
chlorinated lime and whiting reduced to
be purchased at drug stores, chemical
stains, it is more satisfactory to use soa
paste
with
water
may
also
be
used
as
a
supply, or laundry supply houses.
dium hydrosulphite (Na2S204). The surpoulticing material.
If the stain is not bad, grit scrubbing
face should be first soaked with a solution
Some blue inks contain Prussian blue,
powders, commonly used on marble,
made by dissolving 1 part of sodium cia ferrocyanide of iron. These stains
terrazzo and tile floors are often satisfactory
trate crystals in 6 parts water. Dip a white
cannot be removed by the perborate
as a poulticing material. Stir powder into
cloth or cotton batting in this solution
poultice, Javelle water, or chlorinated
hot water until mortar consistency is
and paste over the stains for 10 or 15 minlime poultice. Such stains yield to
obtained. Mix thoroughly, and then apply
utes. On horizontal surfaces, sprinkle over
treatment of ammonia water applied on
to the stained surface in a ½-inch layer.
with a thin layer of hydrosulphite crystals,
a
layer
of
cotton
batting.
Strong
soap
Leave until dry. In most cases, two or
moisten with water, and cover with a stiff
solution applied the same way may also
more applications will be necessary.
paste of whiting and water. On a vertical
be effective.
surface, place whiting paste on a plasterer’s
Indelible ink often consists entirely of
hob, sprinkle on a layer of hydrosulphite,
synthetic dyes. Stains may be treated as
moisten slightly and apply to the stain. ReUrine Stains
outlined above for that type. However,
move after one hour. Do not leave longer
some indelible inks contain silver salts
or a black stain may develop. If the stain
Use the methods outlined for tobacco
which cause a black stain. This may be
is not completely removed, repeat the
stains. Should the stain prove stubborn,
removed with ammonia water applied
operation with fresh materials. When the
saturate cotton batting in liquid and paste
by bandage. Usually several applications
stain disappears, rinse surface thoroughly
over the remaining stain. Resaturate the
are necessary.
with water.
cotton if necessary.
R
T
S
C
U
U
T
e
n
a
m
STRUCTURE magazine
55 January 2008
®
E
R
i
z
a
g
Engineer’s Notebook
By Craig E. Barnes, P.E., SECB
aids for the structural engineer’s toolbox
Removing Stains from Concrete
continued on next page
Fire Stains
Rotten Wood Stains
General Service Stains
Concrete is often badly discolored from smoke
or pitch from burning wood. Sometimes the
appearance may be restored by the following
process: scour with powdered pumice or grit
scrubbing powder to remove surface deposits.
Then make a solution of trisodium phosphate
and chlorinated lime, described for tobacco
stains. Fold a white Canton flannel cloth to
form three or four layers and saturate with the
liquid. Paste this over the stain and cover with
a slab of concrete or glass, making sure the
cloth is pressed firmly against the surface. If on
a vertical plane, devise a method to hold the
flannel and its covering snug against the stain.
Resaturate the cloth as often a necessary. Deep
pitch stains may require several treatments.
Under damp conditions, wood will rot
and cause a chocolate-colored stain which is
readily distinguished from most other stains
by its dark color. The best treatment is that
recommend for fire stains. Action may be
accelerated by first scrubbing the surface
thoroughly with glycerin diluted with four
times its volume of water.
When areas of terrazzo floors become
yellow while adjacent slabs remain free from
discoloration, the trouble is probably due
® Such
to the original finishing of the floor.
discolorations are not usually hard to remove
by poultice methods, or may yield to a surface
scrubbing with Javelle water. Javelle water can
usually be prepared as follows:
Dissolve 3 pounds of washing soda in 1
gallon of water. Mix 12 ounces of chlorinated
lime to a paste in a shallow enameled pan
by adding water slowly. Mash the lumps.
Add the paste to soda solution, make up to
2 gallons by adding water, and place in a
covered stoneware jar to settle. Use the clear
liquid when required, diluting with six times
its volume of clear water. Javelle water is a
strong bleaching material, and should not be
allowed to drop on colored fabrics. It is not
recommended for general cleaning purposes,
but its occasional use on stained concrete is
believed to be entirely safe.
Poulticing with commercial grit scrubbing
powders, such as those used for cleaning marble
floors, will prove satisfactory for removing
most stains of this class. In poulticing with
these, the water material is slowly stirred into
a pail of hot water until a thick paste of mortar
consistency is obtained.▪
Lubricating Oil Stains
R
T
S
Lubricating oils may penetrate concrete. It
should be mopped up immediately, covering
the spot with a dry powdered material such
as portland cement, fuller’s earth, or hydrated
lime. If treated promptly, no staining will
occur. If the oil remains for some time, other
methods may be required.
Make a paste of a solution of 1 pound
trisodium phosphate to 1 gallon of water and
sufficient whiting to thicken. Spread this paste
in a layer about ½-inch thick over the surface
to be cleaned and let it dry (approximately 24
hours). Remove the paste and wash surface with
clear water.
An alternate treatment consists of the
application of a poultice made by adding
powdered talc or whiting to a 5 percent
solution of caustic soda.
Commercial degreasing products also are
available. Some are marketed in aerosol spray
cans. The stain is sprayed with the solution
and flushed with clear water to carry away
the residue.
t
Iodine
igh Stains
pyr
C
U
Coffee stains can be removed by applying a
cloth saturated in glycerin diluted with four
times its volume of water. Javelle water or the
solution used on fire stains is also effective.
a
Secretions from the hands or oil from the
hair may produce stains on concrete. The
stain is brown or yellow and may be mistaken
for an iron stain. The best treatment is that
recommended for fire stains. Bad stains may
require several treatments.
Copper, Bronze and
Aluminum Stains
Copper and bronze stains are nearly always
green, but in some cases may be brown.
Mix dry, 1 part ammonium chloride (sal
ammoniac) and 4 parts powdered talc. Stir
in ammonia water to make a paste. Place
this over the stain and leave until dry. A
stain of this kind that has been collecting for
some years may require several repetitions to
remove it. Aluminum chloride may be used
instead of sal ammoniac.
Aluminum stains appear as a white deposit
which can be removed by scrubbing with a
10 to 20 percent muriatic acid solution. On
colored concrete, a weaker solution should
be used.
STRUCTURE magazine
56
e
n
i
z
a
g
Perspiration Stains
m
Coffee Stains
U
T
Co stain will gradually disappear of
An iodine
its own accord. It may be removed quickly
by applying alcohol and covering with
whiting or talcum powder. If on a vertical
wall, mix talcum to a paste with alcohol,
apply some alcohol to the stain, and then
cover with the paste.
E
R
January 2008
Craig E. Barnes, P.E., SECB, is principal
and founder of CBI Consulting Inc. As an
engineer registered in both the civil and
structural fields, Mr. Barnes has over 40
years experience designing, coordinating, and
managing structural and civil engineering
projects throughout New England. Craig
also serves on the STRUCTURE® Editorial
Board. He can be reached via email at
[email protected].
This article is reprinted with permission
from Portland Cement Association
Publication. I 5214, 1988. Information
contained in this article is derived from
Concrete Information, Portland Cement
Association, Structural Bureau.
patience. It is often a matter of repeating the treatment until the desired results are attained. When the staining matter is
unknown, the treatment may require some experimentation. Many chemicals may be applied to concrete without appreciable injury, but acids or chemicals having an acid reaction should be avoided. Even weak acids may roughen the surface
if left for any length of time. For stains which penetrate, it is necessary to resort to
poultice or bandage. A poultice made by mixing active chemicals with fine inert powder
Treatment of Iron Stains
to a pasty consistency is applied in a thick layer. Bandages consist of cotton batting, or
layers of cloth, soaked in chemicals and pasted over the stain.
Iron Stains can usually be recognized by
their resemblance to iron rust, or by their
t
proximity to steel or iron in the building.
righ
y
p
Large areas stained from using curing waCo
ter containing iron may be improved in
Ink Stains
Tobacco Stains
appearance by mopping with a solution
Different inks require different
The following formula is generally
containing 1-pound oxalic acid powder
treatments. Ordinary writing inks may
effective: dissolve 2 pounds of trisodium
per gallon of water. After 2 or 3 hours,
etch concrete due to acid content. To
phosphate crystals in 1 gallon of hot
rinse with clear water, scrubbing at the
remove a stain of this type, make a strong
water. Mix 12 ounces of chlorinated
same time with stiff brushes or brooms.
solution of sodium perborate in hot
lime to a paste in a shallow enameled
Bad spots may be scrubbed with a second
water. Mix with whiting to a thick paste,
pan by adding water slowly and mashing
application. For deeper stains, the followapply in ¼-inch layer, and leave until dry.
the lumps. Pour this and the trisodium
ing methods may be used.
If some of the blue color is visible after
phosphate solution into a 2-gallon
Method 1: Dissolve 1 part sodium cithe
poultice
is
removed,
repeat.
If
only
a
stoneware jar and add water until full.
trate in 6 parts water. Mix thoroughly
brown stain remains, treat it by Method
Stir well, cover the jar and allow the lime
with equal volumes of glycerin. Mix part
1 for iron stains. Sodium perborate can
to settle. To use, add some of the liquid
of this liquid with whiting to form a paste
be obtained from any druggist.
to powdered talc until a thick paste is
just stiff enough to adhere to the surface
Many red, green, violet and other
obtained. Apply with a trowel as a ¼in a thick coat. Apply with a putty knife
bright colored inks are water solutions
inch poultice. To apply with a brush,
or trowel; this will dry in a few days. It
of synthetic dyes. Stains made by this
add about one teaspoon of sugar to each
should then be replaced with a new layer,
type of ink can usually be removed by
pound of powdered talc. When dry,
or softened by addition of more liquid.
the
sodium
perborate
poultice
described
scrape off with wooden paddle or trowel.
While this treatment has no injurious
above. Often the stain can be removed
This mixture is a strong bleaching agent
effects, its action may be too slow to be
by applying ammonia water on cotton
and is corrosive to metal. Care should be
practical with bad stains. Ammonium
batting. Javelle water is also effective,
taken not to drop it on colored fabrics or
citrate may produce quicker results than
used the same as ammonia water, or
metal fixtures.
sodium citrate, but may injure polished
mixed to a paste with whiting and applied
This method is valuable for treating
surfaces slightly.
as poultice. A mixture of equal parts of
other stains. Trisodium phosphate may
Method 2: For deep and intense iron
chlorinated lime and whiting reduced to
be purchased at drug stores, chemical
stains, it is more satisfactory to use soa
paste
with
water
may
also
be
used
as
a
supply, or laundry supply houses.
dium hydrosulphite (Na2S204). The surpoulticing material.
If the stain is not bad, grit scrubbing
face should be first soaked with a solution
Some blue inks contain Prussian blue,
powders, commonly used on marble,
made by dissolving 1 part of sodium cia ferrocyanide of iron. These stains
terrazzo and tile floors are often satisfactory
trate crystals in 6 parts water. Dip a white
cannot be removed by the perborate
as a poulticing material. Stir powder into
cloth or cotton batting in this solution
poultice, Javelle water, or chlorinated
hot water until mortar consistency is
and paste over the stains for 10 or 15 minlime poultice. Such stains yield to
obtained. Mix thoroughly, and then apply
utes. On horizontal surfaces, sprinkle over
treatment of ammonia water applied on
to the stained surface in a ½-inch layer.
with a thin layer of hydrosulphite crystals,
a
layer
of
cotton
batting.
Strong
soap
Leave until dry. In most cases, two or
moisten with water, and cover with a stiff
solution applied the same way may also
more applications will be necessary.
paste of whiting and water. On a vertical
be effective.
surface, place whiting paste on a plasterer’s
Indelible ink often consists entirely of
hob, sprinkle on a layer of hydrosulphite,
synthetic dyes. Stains may be treated as
moisten slightly and apply to the stain. ReUrine Stains
outlined above for that type. However,
move after one hour. Do not leave longer
some indelible inks contain silver salts
or a black stain may develop. If the stain
Use the methods outlined for tobacco
which cause a black stain. This may be
is not completely removed, repeat the
stains. Should the stain prove stubborn,
removed with ammonia water applied
operation with fresh materials. When the
saturate cotton batting in liquid and paste
by bandage. Usually several applications
stain disappears, rinse surface thoroughly
over the remaining stain. Resaturate the
are necessary.
with water.
cotton if necessary.
R
T
S
C
U
U
T
e
n
a
m
STRUCTURE magazine
55 January 2008
®
E
R
i
z
a
g
Engineer’s Notebook
By Craig E. Barnes, P.E., SECB
aids for the structural engineer’s toolbox
Removing Stains from Concrete
continued on next page
Fire Stains
Rotten Wood Stains
General Service Stains
Concrete is often badly discolored from smoke
or pitch from burning wood. Sometimes the
appearance may be restored by the following
process: scour with powdered pumice or grit
scrubbing powder to remove surface deposits.
Then make a solution of trisodium phosphate
and chlorinated lime, described for tobacco
stains. Fold a white Canton flannel cloth to
form three or four layers and saturate with the
liquid. Paste this over the stain and cover with
a slab of concrete or glass, making sure the
cloth is pressed firmly against the surface. If on
a vertical plane, devise a method to hold the
flannel and its covering snug against the stain.
Resaturate the cloth as often a necessary. Deep
pitch stains may require several treatments.
Under damp conditions, wood will rot
and cause a chocolate-colored stain which is
readily distinguished from most other stains
by its dark color. The best treatment is that
recommend for fire stains. Action may be
accelerated by first scrubbing the surface
thoroughly with glycerin diluted with four
times its volume of water.
When areas of terrazzo floors become
yellow while adjacent slabs remain free from
discoloration, the trouble is probably due
® Such
to the original finishing of the floor.
discolorations are not usually hard to remove
by poultice methods, or may yield to a surface
scrubbing with Javelle water. Javelle water can
usually be prepared as follows:
Dissolve 3 pounds of washing soda in 1
gallon of water. Mix 12 ounces of chlorinated
lime to a paste in a shallow enameled pan
by adding water slowly. Mash the lumps.
Add the paste to soda solution, make up to
2 gallons by adding water, and place in a
covered stoneware jar to settle. Use the clear
liquid when required, diluting with six times
its volume of clear water. Javelle water is a
strong bleaching material, and should not be
allowed to drop on colored fabrics. It is not
recommended for general cleaning purposes,
but its occasional use on stained concrete is
believed to be entirely safe.
Poulticing with commercial grit scrubbing
powders, such as those used for cleaning marble
floors, will prove satisfactory for removing
most stains of this class. In poulticing with
these, the water material is slowly stirred into
a pail of hot water until a thick paste of mortar
consistency is obtained.▪
Lubricating Oil Stains
R
T
S
Lubricating oils may penetrate concrete. It
should be mopped up immediately, covering
the spot with a dry powdered material such
as portland cement, fuller’s earth, or hydrated
lime. If treated promptly, no staining will
occur. If the oil remains for some time, other
methods may be required.
Make a paste of a solution of 1 pound
trisodium phosphate to 1 gallon of water and
sufficient whiting to thicken. Spread this paste
in a layer about ½-inch thick over the surface
to be cleaned and let it dry (approximately 24
hours). Remove the paste and wash surface with
clear water.
An alternate treatment consists of the
application of a poultice made by adding
powdered talc or whiting to a 5 percent
solution of caustic soda.
Commercial degreasing products also are
available. Some are marketed in aerosol spray
cans. The stain is sprayed with the solution
and flushed with clear water to carry away
the residue.
t
Iodine
igh Stains
pyr
C
U
Coffee stains can be removed by applying a
cloth saturated in glycerin diluted with four
times its volume of water. Javelle water or the
solution used on fire stains is also effective.
a
Secretions from the hands or oil from the
hair may produce stains on concrete. The
stain is brown or yellow and may be mistaken
for an iron stain. The best treatment is that
recommended for fire stains. Bad stains may
require several treatments.
Copper, Bronze and
Aluminum Stains
Copper and bronze stains are nearly always
green, but in some cases may be brown.
Mix dry, 1 part ammonium chloride (sal
ammoniac) and 4 parts powdered talc. Stir
in ammonia water to make a paste. Place
this over the stain and leave until dry. A
stain of this kind that has been collecting for
some years may require several repetitions to
remove it. Aluminum chloride may be used
instead of sal ammoniac.
Aluminum stains appear as a white deposit
which can be removed by scrubbing with a
10 to 20 percent muriatic acid solution. On
colored concrete, a weaker solution should
be used.
STRUCTURE magazine
56
e
n
i
z
a
g
Perspiration Stains
m
Coffee Stains
U
T
Co stain will gradually disappear of
An iodine
its own accord. It may be removed quickly
by applying alcohol and covering with
whiting or talcum powder. If on a vertical
wall, mix talcum to a paste with alcohol,
apply some alcohol to the stain, and then
cover with the paste.
E
R
January 2008
Craig E. Barnes, P.E., SECB, is principal
and founder of CBI Consulting Inc. As an
engineer registered in both the civil and
structural fields, Mr. Barnes has over 40
years experience designing, coordinating, and
managing structural and civil engineering
projects throughout New England. Craig
also serves on the STRUCTURE® Editorial
Board. He can be reached via email at
[email protected].
This article is reprinted with permission
from Portland Cement Association
Publication. I 5214, 1988. Information
contained in this article is derived from
Concrete Information, Portland Cement
Association, Structural Bureau.
